Alkaline Rocks and Carbonatites of the World

Setup during HiTech AlkCarb: an online database of alkaline rock and carbonatite occurrences

Potash Sulfur Springs (Wilson Springs)

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Occurrence number: 
174-00-117
Country: 
United States
Region: 
Arkansas
Location: 
Longitude: -93.08, Latitude: 34.5
Carbonatite: 
Yes

This approximately circular complex just over 1 km in diameter intrudes faulted and folded Palaeozoic shales, sandstones and cherts. The complex appears to have a poorly defined ring structure with an outer ring of syenite and fenite and a central area chiefly of nepheline syenite with smaller bodies of ijolite, melteigite, pyroxenite and jacupirangite. Near the centre a breccia with a calcite cement outcrops and carbonatite has been encountered in a number of boreholes. Carbonatite is also present as dykes and irregular masses near the margins of the intrusion. Highly weathered rocks averaging 13 m in thickness cover much of the complex but the outer parts of the nepheline syenite form a low ridge. The fenites are dominated by aegirine which may comprise 80-90% of the rock and these pass into syenites which are probably also fenites, and essentially orthoclase (80-98%) rocks. The nepheline syenites contain alkali feldspar, about 32% nepheline and 7% garnet. The ijolite series varies from rocks with 60% nepheline to jacupirangite with only traces, one variety of which consists principally of biotite with a little magnetite and sphene. Pyroxenite consists of ferro-augite/aegirine-augite with some biotite but the pyroxene in the melteigites is aegirine-augite. One melteigite type contains 30-60% Ti-garnet, which is present throughout the ijolite series. The carbonatites are calcite rocks with accessory biotite, aegirine, magnetite, pyrite and pyrrhotine. Although dykes are common within the complex they are even more abundant within the surrounding sediments and include phonolites, trachytes, ouachitites, monchiquites and fourchites. Apart from the fenites shown on Fig. 170, a thermal aureole extends for a further 300 m or more and involves hornfelsing of shales, while nearer the complex more siliceous rocks contain cristobalite, wollastonite, tremolite, aegirine, miserite and calcite. Palaeomagnetic data will be found in Scharon and Hsu (1969).

Economic: 
The only mining operations specifically for vanadium in the U. S. are based on the Potash Sulfur Springs complex. The vanadiferous ores occur as local concentrations within the metamorphic aureole and include fenite, feldspathic breccias and other metamorphosed sedimentary rocks. The ores contain about 1% V2O5and minerals such as montroseite, fervanite and hewettite have been identified. The area has also been investigated as a Nb and Ti deposit (Fryklund et al., 1954).
References: 

FRYKLUND, V.C., HARNER, R.S. and KAISER, E.P. 1954. Niobium (columbium) and titanium at Magnet Cove and Potash Sulphur Springs, Arkansas. Bulletin, United States Geological Survey, 1015-B: 23-57.
HOLLINGSWORTH, J.S. 1967. Geology of the Wilson Springs vanadium deposits Garland County, Arkansas. Guidebook, Geological Society of America Field Conference, Central Arkansas Economic Geology and Petrology. Arkansas Geological Commission, Little Rock: 22-8.
SCHARON, L. and HSU, I-C. 1969. Paleomagnetic investigation of some Arkansas alkalic igneous rocks. Journal of Geophysical Research, 74: 2774-9

Map: 
Fig. 1_169 Distribution of alkaline igneous rocks and carbonatites in central Arkansas. and Fig. 1_170 Potash Sulfur Springs (after Hollingsworth, 1967, Fig. 7).
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith